钒微合金钢中α-Fe/V_(4)C_(3)界面结构与稳定性的第一性原理计算

First principle calculation of structure and stability ofα-Fe/V_(4)C_(3) interface in vanadium microalloyed steel

为了探讨α-Fe/V_(4)C_(3)的界面稳定性,利用第一性原理平面波赝势方法优化(100)_(α-Fe)/(100)_(V_(4)C_(3))三种不同原子堆积序列(Fe-on-C,Fe-on-V和Bridge)的界面构型。通过界面分离功分析α-Fe/V_(4)C_(3)界面的结构稳定性,计算三种构型的界面分离功分别为4.29,1.43,2.70 eV,分离功越大表明界面稳定性越强,在α-Fe中析出的V_(4)C_(3)主要以Fe-on-C构型存在,其界面稳定性最强。通过态密度,差分电荷密度和电子局域化函数研究α-Fe/V_(4)C_(3)的电子结构性质。结果表明:在Fe-on-C构型中,界面处Fe原子存在电荷贫化区,丢失的电荷转移到界面处,由于C原子具有强电负性,在界面处形成较强的混合离子/共价键,并且Fe和C原子的键合作用明显强于Fe和V原子。通过总态密度和分波态密度发现,Fe-d轨道与C-p轨道在-4.5~-2.5 eV的区域内发生电子轨道杂化,形成Fe—C共价键。

In order to investigate the interface stability ofα-Fe/V_(4)C_(3),the interface structure of three different atomic stacking sequences(Fe-on-C,Fe-on-V and Bridge)of(100)_(α-Fe)/(100)_(V_(4)C_(3)) were optimized by using the first-principles calculations with pseudo potential plane wave method.The structural stability ofα-Fe/V_(4)C_(3) was measured by the work done of separation for the three configurations.The calculated interfacial separation work of the three configurations is 4.29,1.43 eV and 2.70 eV,respectively,which larger interfacial separation work indicating stronger interface stability.Therefore,V_(4)C_(3) precipitated inα-Fe mainly exists in the Fe-on-C configuration,and its interface stability is the strongest.The electronic structure properties ofα-Fe/V_(4)C_(3) were studied by calculating the density of states,differential charge density and electron localization function.The results show that in the Fe-on-C structure configurations,there is a charge-depleted zone for Fe atoms at the interface,and the lost charge transfer to the interface.Due to the strong electronegativity of C atoms,strong mixed ions/covalent bonds are formed at the interface,and the bond and interaction between Fe and C atoms are significantly stronger than that between Fe atoms and V atoms.Meanwhile,according to the total density of states and projected density of states,it is found that the Fe-d orbital and the C-p orbital hybridize in the-4.5 eV to-2.5 eV region,promoting the formation of the Fe—C covalent bond.